Stabilized photographic prehardener compositions



United States Patent Office 3,345,173 Patented Oct. 3, 1967 3,345,173STABILIZED PHOTOGRAPHIC PREHARDENER COMPOSITIONS Howard E. Munro,Rochester, N .Y., assignor to Eastman Kodak Company, Rochester, N.Y., acorporation of New Jersey No Drawing. Filed July 14, 1965, Ser. No.472,048 3 Claims. (Cl. 96-50) This invention relates to photographicprehardener compositions which have been stabilized to prevent formationof peroxide compounds during storage.

It is known that photographic films and papers can be processed toprovide useful photographic records in shorter periods of time thannormal by carrying out the conventional processing steps at elevatedtemperatures, such as 80 to 150 F. However, such high temperatureprocessing requires prehardening of the material to be processed so thatundue softening of the colloid binder layers does not occur and scufiingand marking of the colloid binder layers is minimized.

One very useful means of accomplishing such prehardening is described inthe copending application of Baden, Bard and Seemann U.S. Ser. No.321,323, filed Nov. 4, 1963, now Patent No. 3,294,536. The prehardenercompositions described in the Baden et al. application contain adialkoxytetrahydrofuran, such as dimethoxytetrahydrofuran,diethoxytetrahydrofuran, etc., as the active hardening ingredient. Suchmaterials contain the alkoxyl groups as substitutents on the carbonatoms adjacent to the oxygen atoms. When added to solutions having a lowpH, e.g., 25, these furan compounds decompose to provide succinaldehyde,which is a useful hardening agent, particularly for gelatin layers ofthe type conventionally used in photography, either as a colloid binderfor the lightsensitive silver halide, or in a protective overcoat layer.The succinaldehyde precursor can be used alone to perform hardening orcan be used in conjunction with other hardening compounds, particularlyformaldehyde.

While the dialkoxytetrahydrofuran compounds are quite useful forprehardening purposes, they sufl'er from the disadvantage of formingperoxide upon storage. For example, 2,5-dimethoxytetrahydrofuran isquite useful in prehardening color films and papers, particularly thosecontaining color-forming compounds or couplers within thelight-sensitive layers, but this compound produces undesirable peroxidecompounds it stored for any appreciable time before use, and it isobvious that these peroxide compounds, if allowed to increasesufiiciently in amount, will cause disastrous results when thephotographic material is prehardened in a bath containing a contaminatedtetrahydrofuran compound.

I have found that the deleterious formation of peroxide compounds indialkoxytetrahydrofuran compositions can be completely eliminated orsubstantially reduced if small amounts of a butylated phenol compoundcontaining an alkoxyl radical or an alkyl radical in the position parato the hydroxyl group is added to the tetrahydrofuran compounds beforestorage. For example, amounts as small as 0.025% by weight, based on thetetrahydorfuran compound, have been found to have remarkable results inpreventing such undesired peroxide formation. The quantity of phenolcompound added as a stabilizing agent can vary considerably, dependingupon the purity of the tetrahydrofuran compound, the ultimate use forthe composition, etc. In general, only small amounts are required, but Ihave found that from about 0.025-0.40% by weight, based on the weight ofthe tetrahydrofuran compound is suificient to stabilize suchtetrahydrofuran compounds for substantial periods of time. Largeramounts of phenol stabilizers can be used, although ordinarily there isno advantage in doing so.

It is, therefore, an object of my invention to provide stabilizedphotographic prehardener compositions containing adialkoxytetrahydrofuran compound. Another object is to provide butylatedphenol compounds containing a substituent para to the hydroxyl group,which are particularly useful as stabilizing materials. Another objectis to provide aqueous prehardening compositions which are particularlyuseful in treating photographic color films and papers so that they canbe processed at elevated temperatures without adverse effects. Otherobjects will become apparent from the following description andexamples.

Particularly useful butylated phenol compounds for the purposes of myinvention comprise 2,6-di-tertiary butyl-pcresol, butylatedhydroxyanisole (BHA), etc. These particular phenol compounds areparticularly useful since they are markedly effective in controllingperoxide formation, while at the same time they have little or nodeleterious photographic effects, which might become apparent in usingdialkoxytetrahydrofuran compounds in photographic prehardeningsolutions.

The stabilizing compounds of my invention can be intimately mixed withthe dialkoxytetrahydrofuran compounds in any suitable manner, since suchsmall amounts are employed. For example, a small amount of the stabilizer dissolved in a suitable solvent, such as propylene glycol, canbe added to the dialkoxytetrahydrofuran compound and the mixture runthrough any suitable mixing apparatus, such as a ball mill or the like.In the above described manner, 2,5-dimethoxytetrahydrofuran wasstabilized by the addition thereto of 0.01% of2,6-di-tertiarybutyl-p-cresol. No peroxide formation was evident at theend of one year. This material containing both the tetrahydrofurancompound (DMTF) and the cresol compound was used in the followingexamples:

Example 1 800 ml. of water at 90 F. was used to dissolve 4.30 ml. ofstabilized 2,5-dimethoxytetrahydrofuran, 5.41 ml. of 18 Normal sulfuricacid and 0.5 gram of the sodium salt of para-toleuene-sulfinic acid.This solution was stirred for 10 minutes at 90 F. whereby the DMTFbecame hydrolyzed to succinaldehyde. 153 grams of sodium sulfate and 2grams of sodium bromide were then added and the composition was mixedfor 20 minutes. There was then added 20 grams of sodium acetate and 27ml. of formalin, the volume was then brought to one liter with water andthe pH was adjusted to 4.8 at F. The composition prepared was employedas a prehardener for photographic films containing gelatin-silver halidephotographic emulsions thereon and was found to be an effectiveprehardener prior to the processing of the film in the developing baths.This prehardener composition had the unique prop erty of hardening thegelatin emulsion at a low pH and was very effective within the pH rangeof 4-5.

Example 2 A solution was prepared in 600 ml. of water at F. of 0.10 ml.of octyl alcohol, 4.30 ml. of stabilized 2,5-dimethoxytetrahydrofuran,and 5.41 ml. of 18 Normal sulfuric acid. This solution was mixed for tenminutes after which time 153 grams of sodium sulfate and 2.0 grams ofsodium bromide were added. The solution was then stirred for 20 minutes,whereupon 20 grams of sodium acetate and 27 ml. of 37% formalin andsufiicient water to make the final volume 1 liter were added. The pH wasadjusted to 4.80. This solution exhibited a good prehardening effect andcould usefully be employed without the build-up of polymeric dirt on thefilm or apparatus.

The stabilized compositions of my invention can be used in a number ofphotographic color processes, such as that described in Hanson and VogtUS. application Ser.

No. 209,263, filed July 11, 1962, now Patent No. 3,246,- 987. In usingthe prehardening compositions of my invention in such color processes,it is necessary only to treat the photographic material prior to colorprocessing with an aqueous solution containing my stabilizedtetrahydrofuran compound. The conventional photographic processing stepscan then follow this initial prehardening treatment. One modification inthe conventional color processig which can be employed is to elevate thetemperature so that the speed of the processing is increased, asindicated above.

As illustrated above, the stabilized tetrahydrofuran compositions of myinvention can be employed alone or together with other photographicprocessing compounds, including formaldehyde and the like. Thecompositions can also contain other compounds, such as alkali metalbromides, alkali metal sulfates,.and supplemental stabilizing compounds,such as the alkali metal salts, e.g., sodium, potassium, etc., ofaromatic sulfinic acids, such as benzenesulfinic, p-toluenesulfinic,salicylsulfinic, chlorobenzenesulfinic, etc., acids. The quantity ofdialkoxytetrahydrofuran compounds used in the prehardening bath itselfcan vary, although I have found that about 0.5 to 50 grams per liter aresufiicient. The stabilized tetrahydrofuran compounds of my invention canalso be employed in conjunction with compounds having fog-inhibitingproperties, such as those described in Graham U.S. application Ser. No.351,218, filed Mar. 11, 1964. Typical antifoggant compounds described inthe application, which are useful in my invention includeN-methylbenzothiazolium-p-toluenesulfonate, as well as otherwater-soluble benzothiazolium salts, including those having other alkylsubstituents on the nitrogen atom thereof (e.g., ethyl and the like).Also useful as antifoggants when used in conjunction with mytetrahydrofuran compounds are benzothiazolium salts containing twobenzothiazole nuclei joined together through an alkylene radicalattached through the nitrogen atoms thereof. Water-solubilizing acidanions comprise perchlorate, toluenesulfonate, etc. In general, theprehardening solutions containing both the 4 tetrahydrofuran compoundsof my invention and the benzothiazolium antifoggants can contain fromabout 1 to 200 mg. per liter of the benzothiazolium salt.

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention as described hereinabove and as defined in the appendedclaims.

What I claim as my invention and desire secured by Letters Patent of theUnited States is:

1. A composition comprising a dialkoxytetrahydrofuran compound,formaldehyde, an alkali metal salt of an aromatic sulfinic acid and atleast 0.025% by weight, based on the tetrahydrofuran compound, of astabilizer selected from the class consisting of butylatedhydroxyanisole and butylated hydroxytoluene.

2. An aqueous photographic prehardener composition containing from 0.5to grams per liter of 2,5-dialkoxytetrahydrofuran, formaldehyde, and atleast 0.01% by Weight based on the said tetrahydrofuran compound of2,6-di-tert.-butyl-p-cresol.

3. In a photographic prehardener composition containing from 0.5 to 50grams per liter of 2,5-dialkoxytetrahydrofuran, and formaldehyde, theimprovement comprising the use of 2,5-dialkoxytetrahydrofuran stabilizedagainst the formation of peroxides with at least 0.01% by weight, basedon the said tetrahydrofuran compound, of a stabilizer selected from theclass consisting of butylated hydroxyanisole and butyaltedhydroxytoluene.

References Cited Lundberg, W. 0.: Autoxidation and Antioxidants, NewYork, Interscience Publishers, 1962, vol. II, pages 498- 503.

NORMAN G. TORCHIN, Primary Examiner.

C. E. DAVIS, Assistant Examiner.

1. A COMPOSITION COMPRISING A DIALKOXYTETRAHYDROFURAN COMPOUND,FORMALDDEHYDE, AN ALKALI METAL SALT OF AN AROMATIC SULFINIC ACID AND ATLEAST 0.025% BY WEIGHT, BASED ON THE TETRAHYDROFURAN COMPOUND, OF ASTABILIZER SELECTED FROM THE CLASS CONSISTING OF BUTYLATEDHYDROXYANISOLE AND BUTYLATED HYDROXYTOLUENE.